This invention relates to an improved vane type pump used for vacuum pumping, air pumping and the like.
In a conventional vane type pump, a cylindrical housing having inlet and outlet ports is secured to a structure such as the frame of an automotive generator. The housing has a cylindrical inner surface, one end being open and the other end being closed. A rotor is eccentrically disposed within the housing, and is mounted on the generator shaft. The rotor has a plurality of radial slots in its peripheral surface, in which a plurality of vanes are slidably disposed.
When the rotor is driven by the shaft the vanes are forced outwardly by centrifugal force into free sliding engagement with the inner surface of the housing, and as the vanes rotate in the housing air is sucked from the inlet port and discharged through the outlet port under a pumping action. The inlet port may be connected to a vacuum tank, for example, and the sucking of the air through such port will evacuate the air from the tank. To maintain good sliding conditions between the outer edges of the vanes and the inner surface of the housing lubricating oil is supplied to the contact surface between them.
When such a pump is operated at high speed or without sufficient lubricating oil, the outer edges of the vanes soon become worn due to their friction with the inner surface of the housing. If the vanes are made of carbon the outer edges tend to break off due to the decreased bonding between the carbon particles caused by the friction induced heating.